1. Field of the Invention
The present invention pertains to deep fat frying machines and in particular to such machines having semiautomatic capability for initiating and terminating a cooking cycle. The present invention also pertains to air filters for deep fat frying machines and the like.
2. Brief Description of the Prior Art
Deep-fat fried foods are enjoying increasing popularity today. Typically, large institutions, restaurants and the like maintain a vat or vessel of heated cooking oil during periods of anticipated use so that a cook need only prepare the food to be deep-fat fried, load the prepared food into an open wire basket and immerse the basket in the vat to initiate a cooking cycle. One example of a heated vat for a deep-fat food fryer is given in U.S. Pat. No. 2,212,905, which includes a system for circulating the hot fat for filtering thereof, during its use. However, the fryer, intended for use by a cook or other trained personnel, requires manual insertion and extraction of a basket to initiate and terminate a cooking cycle. Further, the fryer requires a custom installation in a kitchen, including external ventilation, and has a minimum of controls and safety-related features.
U.S. Pat. No. 2,222,314 discloses a deep-fat frying cooking machine with a mechanized apparatus for raising a food-carrying basket from a vat of heated fat when a predetermined temperature in the vat is attained, an event from which completion of the cooking cycle is inferred. Also disclosed is a time delay for delaying raising of the basket after the temperature is reached. As with the previously-mentioned frying machine, the machine of U.S. Pat. No. 2,222,314 requires a custom installation in a kitchen, and an external ventilation system. The machine has a minimum of safety-related features, and lacks a more sophisticated cooking control system need for minimum cooking times and for a faster response of the heating system during a cooking cycle.
U.S. Pat. No. 2,753,436 discloses a tabletop deep fat fryer of the type adapted for domestic household and restaurant use, including a heat anticipator for the heat controlling element. The anticipator, consisting of a glow coil, anticipates the heat level given off by the main heating element. The arrangement maintains a substantially constant temperature for a maximum food capacity in a fat-containing well of limited size.
U.S. Pat. No. 2,868,112 provides another example of a semiautomatic deep-fat frying cooking machine having a motor-driven mechanism for raising and lowering a foraminous basket. The mechanism includes a vertically-extending guide channel in which a vertically-extending wire loop rides. The loop has an upper hook portion which receives a loop formed at one end of the foraminous basket. The basket also includes horizontally-extending stub-like wire portions which slide against one side of the vat, to maintain the basket in a stable, generally horizontal position as the upper corner thereof is raised and lowered by the sliding linkage mechanism. The motor-driven mechanism contacts the bottom of the vertically-extending elongate link. As the bottom of the link is raised and lowered by the motor-driven mechanism, the upper hook-shaped end, engaged with the basket, follows. Contact between the stub-like wire ends and the vessel sidewall is objectionable, particularly over repeated use and repeated cycling of the lowering mechanism. Further, the cooking machine is designed for a customer installation in an open area, having external ventilation means.
Another arrangement for raising and lowering a basket in a deep-fat fryer using a motor-driven mechanism is disclosed in U.S. Pat. No. 3,217,633. A food-containing basket has a downwardly-extending hook-like loop at one end. The frame for hanging the basket is mounted for movement in vertical directions, and is located against one wall defining a vat of a deep-fat fryer. The basket hanger includes generally-horizontally extending rods, an upper rod for receiving the hook-like loop of the basket and a lower rod for contacting a lower portion of the basket front wall, underneath the hook-like loop. The arrangement requires a relatively large floor-mounted unit for use in an open space having external ventilation. A considerable amount of vertical room above the back of the fryer is required, particularly when the basket frame moves the basket to an elevated position. As with the mechanism of U.S. Pat. No. 2,868,112, the mechanism and food-containing basket are reciprocated in generally vertical directions. Although the basket frame of U.S. Pat. No. 3,217,633 provides a generally more stable mounting of the basket, it requires that the lower end of the frame be either immersed in the oil during cooking or suspended just above the oil, where oil and food particles which cling to the frame become hardened, presenting difficulty in cleaning.
U.S. Pat. No. 3,685,432 discloses an automatic vending machine for deep-fat fried potatoes. A relatively complicated and bulky conveyor system moves a food-containing basket along a relatively complicated path, which not only moves the basket into and out of heated oil, but also tips the basket into a dispensing chute. The conveyor is impractical for semiautomatic partially attended operation. The basket is suspended by a pair of opposed, laterally extending rod-like members. A second basket, generally triangular in lateral cross-section, is used to immerse the uncooked potatoes in a vat of cooking oil. The second basket is rotatable about an horizontal axis. An extension of the basket beyond the axis is connected to an outer periphery of a drive disk which when rotated, levers the basket about a shaft aligned the axis of rotation. It is difficult to control smaller jerking movements of the basket as it is raised and lowered by the eccentric drive disk. The basket is unconnected to the shaft, and merely bears against the shaft with a rolling motion. Since the vending machine is designed for fully unattended operation, it is essential that the frying basket remain in continuous engagement with the drive mechanism for raising and lowering the basket into the fat-containing heated oil. The cooked potatoes are discharged from the frying basket by driving the basket to approach an overturned condition, whereupon the bottom of the basket is beat with a hammer mechanism. The automatic vending machine is fully enclosed, and therefore requires a ventilation system. A filter is provided in front of a fan to remove vapors from the exhausted air.
U.S. Pat. No. 3,818,820 discloses a dispensing apparatus for french-fried potatoes. A generally ladle-shaped member has a lower cavity for receiving uncooked potatoes and for immersing the uncooked potatoes in a vat of heated oil. The handle-like portion of the ladle is trough-like in shape in cross-section, and provides a funnel to guide cooked potatoes toward a destination point. The ladle-like member has a pivotal mounting along the handle-like portion and is tipped back and forth where, in a first direction, the cavity-defining end is immersed in heated oil and, in the other direction, the cavity is discharged into the funnel-like handle, which is inclined away from the vat. The apparatus is designed for use in a fully automated machine and requires a relatively large volume surrounding the ladle-like member because of its geometric shape and movable mounting.
U.S. Pat. No. 3,975,997 discloses a deep-fat fryer which automatically raises and lowers a food-containing basket in a vat of heated oil. A mechanism for moving the basket includes a second, outer basket permanently mounted to the vat through a complex series of linkages for rocking and translating the outer basket. The mechanism includes a number of moving parts immersed in the oil and thus presenting a cleaning problem. The mechanism is relatively costly to produce.
U.S. Pat. No. 4,520,717 discloses a deep-fat food frying apparatus enclosed in a cabinet and having a heated vessel for containing the fat, above which is disposed a cylindrical paper filter with a charcoal element in the central hollow portion thereof. The filter is relatively bulky, and provides a relatively simple, short path for the air traveling therethrough, thus requiring relatively short residence time within the filter. A food-containing basket having a pair of laterally-spaced downwardly-extending handles is positioned at its rear or trailing end. The basket is inserted into the enclosed cabinet, above the cooking oil, as the downwardly-extending handles are aligned with and inserted in handle-engaging brackets mounted on a rotating drive shaft. Thus, both handles must be concurrently engaged with the drive shaft before an operator can release the basket. The mounting and demounting of the basket is somewhat awkward, given the small confined space within the cabinet.